1. Field of the Invention
The present invention relates to a musical tone signal generating apparatus, and more particularly to a musical tone signal generating apparatus which generates a musical tone signal based on stored waveform data.
2. Prior Art
Japanese Utility Model Laid-Open Publication No. 55-60191 discloses the conventional musical tone signal generating apparatus which synthesizes the musical tone signal by use of plural musical tone control parameters.
More specifically, this conventional apparatus provides two waveform memories each storing different waveform data. The data from the two waveform memories are multiplied by the musical tone control parameter, i.e., a note scaling parameter. Thus, the conventional apparatus forms data for two intermediate waveforms whose amplitudes vary in response to the tone pitch. Then, the data of the two intermediate waveforms data are added together, resulting in that data of one waveform is synthesized. The synthesized waveform data has a waveform which is different from the waveforms originally stored in two waveform memories.
However, this conventional apparatus is disadvantageous in that the synthesized musical tone waveform signal can only offer monotonous variation because the conventional apparatus can merely interpolate two waveforms. For this reason, the conventional apparatus cannot generate a musical tone having various representations.
Actually, the conventional apparatus can use only one musical tone control parameter, i.e., note scaling parameter. As a result, the synthesized musical tone waveform signal cannot offer the complicated variation in tone color, by which the conventional apparatus cannot represent various musical scenes.
Meanwhile, Japanese Patent Laid-Open Publication No. 60-147793 discloses another conventional musical tone signal generating apparatus which can alter the tone color with elapsed time.
In this apparatus, continuous musical tone waveforms of some periods are subject to the sampling process and then stored in the waveform memory as the musical tone waveform of the attack portion. In addition, as the musical tone waveform succeeding the attack portion, plural segment waveforms each corresponding to one period are subject to the sampling process and then stored in the waveform memory. Thereafter, a pair of two segment waveforms is read out, and the read waveform is changed at every predetermined time interval by use of the so-called "cross-fade" method. Thus, the tone color to be sounded is varied.
However, the above-mentioned conventional apparatus is designed to merely read the waveform data from the waveform memory in accordance with the predetermined program, which makes the tone color variation monotonous.
In addition, this conventional apparatus changes the waveform by the cross-fade method at every predetermined time interval, which cannot offer delicate tone color variation of the electronic musical instrument to be performed.
Further, when playing the non-electronic musical instrument, the intensity level of the musical tone (i.e., envelope level of the musical tone) is varied with elapsed time. In addition, the tone color is slightly varied in response to the variation in the intensity level of the musical tone. This is the condition by which the non-electronic musical instrument can offer great representations.
Furthermore, pitch variation is made in order to apply musical effects such as initial-touch and after-touch effects to the musical tone. In this case, if the pitch variation and tone color variation can be simultaneously given to the musical tone, it is possible to obtain the musical tone having great representations. In fact, in the non-electronic musical instrument, when the pitch is varied, the tone color is also slightly varied. Therefore, an electronic musical instrument that can simulate the above-mentioned features of the non-electronic musical instrument is desired.